Impact of interfacial coupling of oxygen octahedra on ferromagnetic order in La(0.7)Sr(0.3)MnO(3)/SrTiO(3) heterostructures

La(0.7)Sr(0.3)MnO(3), a half-metallic ferromagnet with full spin polarization, is generally used as a standard spin injector in heterostructures. However, the magnetism of La(0.7)Sr(0.3)MnO(3) is strongly modified near interfaces, which was addressed as “dead-layer” phenomenon whose origin is still controversial. Here, both magnetic and structural properties of La(0.7)Sr(0.3)MnO(3)/SrTiO(3) heterostructures were investigated, with emphasis on the quantitative analysis of oxygen octahedral rotation (OOR) across interfaces using annular-bright-field imaging. OOR was found to be significantly altered near interface for both La(0.7)Sr(0.3)MnO(3) and SrTiO(3), as linked to the magnetism deterioration. Especially in La(0.7)Sr(0.3)MnO(3)/SrTiO(3) superlattices, the almost complete suppression of OOR in 4 unit-cell-thick La(0.7)Sr(0.3)MnO(3) results in a canted ferromagnetism. Detailed comparisons between strain and OOR relaxation and especially the observation of an unexpected La(0.7)Sr(0.3)MnO(3) lattice c expansion near interfaces, prove the relevance of OOR for the magnetic properties. These results indicate the capability of tuning the magnetism by engineering OOR at the atomic scale.